1. Field of the Invention
The present invention relates to a rotation table provided in a tool machine, and particularly, to a rotation table device with an air purging structure.
2. Description of the Related Art
There is a case in which a cutting fluid used in a tool machine may cause degradation such as swelling or hardening in a synthetic resin material of a seal packing or a coating of a cable. In a rotation table device provided on a table of a tool machine disclosed in JP-A 2012-202484, a problem arises in that an insulation material of an electric component disappears due to the intrusion of a cutting fluid when a seal member formed of a synthetic resin material is degraded. As a general method of preventing this problem, there is known a method of preventing the intrusion of a cutting fluid by supplying air into a casing of a rotation table device so that the pressure inside the casing is set to be higher than the atmospheric pressure at all times.
FIGS. 7 to 10 are views illustrating a rotation table device. FIG. 7 is a view illustrating a cross-section of the rotation table device of the related art (an unclamped state). FIG. 8 is a partially cross-sectional view of FIG. 7. FIG. 9 is a view illustrating a cross-section of the rotation table device of the related art (a clamped state). FIG. 10 is a partially cross-sectional view of FIG. 9.
In general, a rotation table device 100 includes a clamping mechanism. In the clamped state, the clamping mechanism moves a braking member 2 formed as a piston or a diaphragm by a fluid such as air or oil toward a target braking member 4, so that a brake disk 3 fixed to a rotation member 16 is pressed against the target braking member 4 fixed to a casing 15.
In the unclamped state, minute gaps 7 and 8 (see FIG. 8) are respectively formed between the braking member 2 and the brake disk 3 and between the brake disk 3 and the target braking member 4 in a non-contact state, and air for air purging passes through the gaps so that the air purging is performed on the entire area inside the clamping mechanism. As a result, it is possible to prevent the intrusion of the cutting fluid.
However, in the clamped state, the braking member 2 comes into press-contact with the brake disk 3 and the brake disk 3 comes into press-contact with the target braking member 4, so that the gap as the passage of the purge air is blocked. That is, the air for the air purging may not flow forward from the contacting braking member 2, and hence spaces 9 and 10 not receiving the air purging pressure are formed (see FIG. 10). As a result, there is a concern that the cutting fluid may intrude into the space not receiving the air purging pressure.